1. Field of the Invention
This invention relates to a process for the manufacture of polyether polyols from polyols and alkylene oxide.
2. Background
The invention relates to a process for the manufacture of polyether polyols by reaction between an organic compound containing 2 or more active hydrogen atoms in the molecule and an alkylene oxide in the presence of an amine catalyst. Such polyether polyols are suitable starting materials for the production of polyurethanes.
As used herein the term "active hydrogen atom" means a hydrogen atom capable of reacting according to the Zerewitinoff reaction.
It is well known to carry out the above-mentioned oxyalkylation reaction using as catalyst an organic amine, and preferably a tertiary amine, such as a trialkylamine. See, for example, U.S. Pat. No. 3,357,970, issued Dec. 12, 1967. However, it has been found that under such conditions the reaction requires in many cases a comparatively long induction period, which can be reduced by including in the reaction system a certain amount of water but this procedure is not desirable if a high functionality (i.e., the number of hydroxyl groups per molecule) of the resulting product is aimed at. Other disadvantages of carrying out the oxyalkylation reaction under the above-mentioned conditions include a rather low reaction rate, even after the induction period, and comparatively high alkylene oxide losses unless large catalyst quantities are used.
It has now been found that the disadvantages described above can be circumvented by the use, as catalyst or catalyst component, of a tertiary amine of a special structure, namely one in which at least one of the carbon atoms attached to the nitrogen atom forms part of a non-aromatic ring structure whilst the other carbon atoms attached to the nitrogen atom do not form part of that ring structure.
It is perhaps useful to add that the use of such amines as catalysts in the formation of polyurethane foams has been known for a long time. It is therefore surprising that their catalytic activity in the oxyalkylation reaction has not been described before.